1. Field of Invention
This invention relates to wire bale ties for use in binding compressed material to form a bale.
2. Description of Prior Art
As more fully set forth in U.S. Pat. No. 3,477,363 of C. D. Trumbo, issued Nov. 11, 1969, cotton is baled by holding it in compressed condition in a conventional baling press and, while it is so held, passing around the compressed mass a number of bale tie wires of a type having interengageable loops at opposite ends. The loops of each tie wire are then brought into alignment with each other transversely of the wire axis and are interengaged by movement of the end portions of the wire transversely of the wire axis. The loops are of such a nature that when the baling pressure is released, the expansion of the cotton mass applies tension to the bale tie wires endwise thereof sufficiently to pull the interengaged loops of each tie wire into a tight knot.
Experience has demonstrated that the fracture or breakage of such bale tie wires most generally occurs in the knotted portion. This failure apparently is due to the weakening of the wire and resultant reduction in its load capacity due to bending it into the loops and pulling the loops into knots. Thus the load capacity of the knot is less than the load capacity of the unknotted portion of the wire. The term load capacity, as applied herein to the knot and to the wire, means the maximum load which can be withstood without breakage when the load is applied as a direct tensile pull on the wire. Necessarily, for forming such loops, and eventually knots, as a result of the expansion of the material after release of the press, certain ductility is required in the wire itself. A compromise is made between the optimum ductility of the wire, required for readily forming the loop and knot and for bending about the bale, and the ability of the knot to withstand the tensile pull on the wire resulting from the expansion of the baled material upon release by the press. Accordingly, in order to assure a knot of the required load capacity with a wire of sufficient bendability, the wire used is of larger cross section throughout its length than it needs to be merely to withstand any direct tensile stresses imposed on the portion of the wire between the knotted ends by the expansion of the baled material.
Again, while ready bendability of the wire about the bale is desirable, it is necessary also that the wire have adequate load capacity to resist elongation under the forces continuously imposed by the baled material.
Heretofore attempts were made to overcome the weaknesses in prior bale ties by using a wire of given physical properties for the midportion of a wire tie and a wire of different physical properties, such as wire annealed for higher ductility and butt welded to the ends of the wire forming the intermediate portion to provide the loop forming portions. For example, in U.S. patent to Rowe, U.S. Pat. No. 1,980,503, in order to obtain the ductility of the end portions without the necessity of annealing the entire wire only the end portions were annealed. In a modification an annealed length of wire was butt welded to the ends of the latter for forming the loops. However, this is very expensive and seems to have the disadvantage of a very abrupt change from one cross section to the other with consequent concentration of stresses and weaknesses.
Another attempted solution was to enclose the end portions of the wire in sleeves to increase the thickness and size of the cross section, as described in the German patent No. 1,015,740, of Sept. 12, 1957.
Recently various laws have been passed limiting the total weight of baling material that can be used in relation to the weight of the bale itself. Concurrently, there has been a considerable increase in the price of wire.
Because of the factors hereinbefore set forth, conventional wire ties have a number of disadvantages. Due to the large cross sections of their intermediate portions, they are difficult to bend as readily as desired about, and in close conformance to the periphery of, the compressed material; and, therefore, they do not lie snugly against the material while it is held compacted by the press. Consequently, longer wire ties are necessary than would be the case did wire ties embrace the material tightly before its release by the press. They employ the inherent characteristics of the metal inefficiently and so require a further excess of metal, thereby increasing the cost. Due to the round cross section, they tend to cut the material in the outer strata of the bale.
The optimum bale tie is one which (a) can be bent readily into firm contact throughout its length with the material while the material is held compressed by the press, (b) presents a relatively flat surface against the outer surface of the baled material so as not to damage or cut into the baled material, and (c) employs the metal with better mechanical efficiency so that the load capacity of the resultant knot and that of the portion of the wire tie between the knotted ends, insofar as concerns resistance to the tensional forces applied on the wire by the baled material, more nearly approach each other than in prior ties, and (d) requires much less metal for a given bale.